2002ApJ...565L.105H

We report the first detection of thermal water vapor emission in the 557 GHz, 1₁₀-1₀₁ ground-state transition of ortho-H₂O toward VY Canis Majoris. In observations obtained with the Submillimeter Wave Astronomy Satellite, we measured a flux of ∼450 Jy, in a spectrally resolved line centered on a velocity v_LSR=25 km.s^–1 with an FWHM of ∼35 km.s^–1, somewhat dependent on the assumed line shape. We analyze the line shape in the context of three different radial outflow models for which we provide analytical expressions. We also detected a weaker 557 GHz emission line from W Hydrae. We find that these and other H₂O emission-line strengths scale as suggested by Zubko and Elitzur.